Hammer mill



Jan. 1.4, 1941. y I .s,.p, HARTSHQRN v 2,228,351I

f HAMMER MILL j `r l Filed July/1s, 1915s 2 Smets-sheet 1 fr n?. @uvam-ong v' y 'vZQwnMZl B JL@ #f2- y ATTORNEYS Jan# j14, 1941. S. D. HART'sl-loRNVV HAMMER MILL Filed July. 18' 1936 2 Shiitspsheet 2 ATTORNEYS Patented Jan. 14, 1941 UNITED, STATES PATENT ornca HAMMER MILL Application July 1s, 193s, serial No. 91,259

8 Claims.

This invention relates to crushing equipment, and more particularly to that class of equipment known as hammer mills, adapted for crushing or breaking hard material such as coal, stone, 'and the like.

The principal object of this invention is to provide a machine operating with high efciency to furnish -a uniform grade of the crushed or broken product.

In ac-cordance with this inven-tion, the rotating drum is provided with a crushing cage colmprising a number of solid rib-like anvil members extending longitudinally, and' perforated scoop-shaped members which join the adjacent anvil members to form the cage. The rotating hammer mechanism is located within t'his cage and operates to impel the material to be crushed against the anvil members. The crushing cage is so constructed vthat substantial parts thereof, including the'anvils, present surfaces substantially perpendicular to the direction of motion of the hammers. By reason of this arrangement, material impelled by the hammers strikes these surfaces from a direction perpendicular thereto, thereby producing a relatively-uniform breaking up of the material attended by a relatively small degree of undesirable chipping or pulverizing.

The scoop-like members of the rotating cage serve to pick up the material and feed it to the hammers'. When .the material is broken to `small enough masses these smaller masses pass out of the cage -through the perforations in the scoops.

A second screen located beyond the perforated scoop-like members makes Ia further selection of the material. An auxiliary drum or compartment is provided with apassageway'for returning the oversize material into the crushing cage w-here it is further broken by the hammer mechanism.

A feature resides inthe symmetryv of the parts whereby the machine may be rotated in either direction. By virtue of this symmetry, when one set of hammer faces or anvil surfaces wears out, rthe machine may be oper-atedv in the reverse direction until the opposite faces or surfaces Wear The machine is provided with a stationary Fig. 1 is a front elevation, in section, of a machine embodying the invention;

Fig. 2 is a side sectional View, taken at line-s 2-'2 of Fig. 1; and

Fig. 3 is a side sectional View, -taken at line 3-3 of Fig, 1.

The machine illustrated in the drawings comprises a drum I0 mounted for rotation in bearings II and I2, at each end thereof. The drum I0 comprises a circular head I3 at one end, and a mouth I4 at the opposite end. The mouth has the general form of a conical frustrum taperingtoward bearing II, and comprises, at the wide inner end, an annular ange I5 parallel with head I3. The flange I5 has a somewhat larger outside diameter than the head I3. The head and mouth are maintained in proper spaced relation by heavy spacer members I 6 attached between the head and the flange I5.

The spacer members, preferably castings, are beams having a cross section in the general form of Wide curving Vs as sho-Wn in Fig. 2. Each spacer beam comprises a heavy solid rib I'I centrally located between a pair of outwardly curving wings I8, which are perforated by numerous holes I9 to form a coarse perforated grate. The spacer beams are provided with end webs 20 in which are drilled holes 2| to permit bolting to the flange I5 land head I3. The arrangement o-f the spacer rbeams is'such that .the wings thereof abut, as shown in Fig. 2, to form a continuous enclosure or cage, between the mouth and the head. Each Vwing forms with the abutting Wing of the adjacent spacer beam an outwardly dished portion which operates as a scoop or lifting shelf when the drum is rotating.

A sieve 22 in the form of a conical frustum, extending between the outer circumferences of the head I3 and of the ange I5, forms the outer surface, or periphery, of the drum.

The central portion of the head I3 is formed into a hub 23 which is babbitted and held within bearing I2. This bearing is constructed to act as a thrust bearing as well as arotary be'aring. The small end of the mouth portion III is likewiseI formed into a hub 24 which is held by bearing II. I i

The drum is enclosed by a stationary cover frame comprising circular heads 25 and 26 positioned at the ends of ythe screen 22, 4and a partially cylindrical wall 2l extending between, and fastened to, these heads. The cylindrical wall surrounds the drum and recedes into a receiving vconduit or a pit 28 beneath.

The mouthof the drum is provided with a strong outwardly extending flange 30 provided with strengthening webs 3l. The front of Ithe flange supports -a .ring gear 32 and the back of the -ang carries an auxiliary drum 33 of large .diameter and-relatively small axial length. The

ing member 38 attached to the head 25. I'his l' construction of the auxiliary drum 33 provides` an annular cavity,v or compartment, 31 defined by head 34, cylinder 33, wall 25, and the outer surf-ace of mouth I4 including ange I5.

The mouth I4 of the drum is lined on the inside with plates 48 and 4| having an opening formed through them, which is covered by a trap door 42 hinged at 42a. A passageway 18 formed by walls 1I connects the Itrap door 42 with an opening 38 in flange I5, adjacent screen 22. vWhen the trap door is at the lower side of the mouth as shown in Fig. 1, it is maintained closed by its own weight. But when the drum rotates 180 degrees so that the door is at the top the door opens inwardly due to its weight and the weight of the material on' it; and any material which has entered passageway 18 through opening 38 when it was at the bottom, drops through the trap door into the mouth of the drum. If desired a spring may be connected with the hinge on the trap door and the strength of the spring so adjusted that the door will not open until it arrives practically at the top, or if desired, until some predetermined amount of material has accumulated in passageway 10 sufficient to push the door open when it arrives at the top. Such a spring arrangement will prevent any undesirable opening due to gravity when the door is at some intermediateA position between the top and the bottom.

A large feed pipe 48 is fitted within the mouth hub which extends into bearing I I. I

A hammer mechanism is provided as follows:

A shaft 45, held by 'a bearing 48, and a rollerv bearing 41 extends centrally into the cage of the drum through the hub 23. To hold the shaft in position a sleeve 48 is forced within the hub; and within the sleeve 48 there is ntted the outer guide 48 of the roller bearing 41. A retaining sleeve 58 provided with a flange 5I for attachment to sleeve 48 serves to hold the roller guide 48 in position. The inner roller guide 52 is forced over a tapered portion of shaft 45 and held in position by a retaining sleeve 53 fastened to the shaft by a nut 54. Sufficient space is left between the contiguous` surfaces of sleeves 58 and The hammer mechanism assembly comprises a number of flanged spacers 51, each having a cylindrical portion 58 and a iiange 58 at one end. The spacers are placed uniformly on the shaft 45, as shown, so that the flanged end of one abuts the uniianged end of the next. A flanged washer III abuts against the end spacer at the free end of the shaft, and a nut BI tightened down on the washer compresses the spacers between the washer and a collar 82 integral with the shaft. A cap 83 placed over washer 80 ser-ves Ato keep grit away from the nut-6I.

Several rods -84 (4 in this case); 'are extended..

longitudinally through' suitable holes l,in the flanges 58 at spaced intervals, and fastened in place in a suitable manner. Hammers 85 having hammer heads 88 are pivoted on the rods 84 within the` spaces between adjacent ilanges 58.

In operation, the hammer shaft 45 is rotated by an external source of power; and the drum is likewise rotated by an external source of power by means of `a pinlonwhlch-"engages the ring gear 32. "The externalsources of power are not shown. The drum and the hammer shaft are preferably rotated in the same direction; and the hammers are rotated considerably faster than the drum. It ispossible, however, to ro' tate the drum and hammer in opposite directions. The Amaterial to be broken is fed from the feed pipe 43 into the mouth 'I8, from whence it enters the crushing cage. 'I'he rotation of the hammer shaft causes the hammers 55 to extend out radially; and the hammer heads strike masses of the material, knocking them against the walls of lthe surrounding cage. A large proportion of these pieces strikes the solid ribs I1, which act as anvils serving to break up the material.

, Those pieces of the material which are broken small enough pass through the holes I8 and into the cavity 38 between the cage and the screen 22. 'I'he centrifugal force due to the rotation facilitates this passage through the perforations. Those pieces which are still too large to pass through the holes in the cage are picked up by the dished scoops formed by the abutting wing members I8, and dropped vdown on the'hammers again, where the breaking process is continued. 'I lie material, while being broken, passes through the cage (from left to right in Fig. 1) and before it reaches the end at head I8, practically all of it should be broken small enough to pass through the holes in the cage. It is noted that holes I8 are tapered outwardly; this minimizes wedging of material in the holes, and prevents clogging.

The material which has been passed through to chamber 38 is thrown against the conical screen 22 and starts to slide endwise Atoward the mouth flange I5. During this sliding the material is selected by the screen 22 which contains holes smaller than holes I8 of the cage: and the material thus selected drops into the pitl 28. All the material which is unable to pass through the screen 22 passes through the opening 38 into the passageway 10 in a drum 33, when opening 38 Ls at the bottom. 'When opening 38 and trap door 42 move to the top this material in passageway 18 drops through the trap door. into the mouth I8, from where it passes into the crushing cage and is further reduced in size.

Uncrushable material which is present, auch as tramp iron, finally lodges in the end cavity 81 from where it may be removed from time to time.

It has been vfound that the breaking or crushing action is most satisfactory when the individual masses of the material are impelled by the hammers against surfaces which lie in a plane perpendicular to the direction in. which the masses are impelled. This type oi' action results in the most effective kind of breaking and yields a product which is relatively uniform and free of chips. Furthermore, material impinging against a surface creates much less abrasion on that surface when it is perpendicular .than when it is oblique tothe path of the material.

The machine .of this invention is designed to perform the desired type of breaking action .by which there is obtained a high degree of clean breaking and a minimum of chipping. This desired action arises from the peculiar form of the crushing cage relative to the position of the,ham mers, whereby there is presented a relatively large `crushing surface of the'cage substantially perpendicular to the direction of motion of the hammers. This large perpendicular crushing surface is constituted by that part of the anvils Il facing the approaching hammers and the party of the perforate scoop, or Wing, portions contiguous to the anvils. Masses of the material projected by a hammer fly toward the cage in the direction of motion of the hammer, i. e. tangential to the circle described by the moving hammer; and a large proportion of these masses strikes the anvils'l'l which break it into relatively uniform sizes.

The use of the double selecting, or screening,

. apparatus has a marked advantage over a single screen, for by reason of the relatively large perforations of the cage, or inner screen, small particles are quickly removed'from the crushing cage so that they do not interfere with the crushing action on the remaining larger pieces and are not ground undesirably small. At the same time the proper size selection is provided by the outer screen of ner mesh.

It is noted that the machine is constructed in a manner to reduce to a minimum the expulsion of dust which is created during the crushing opjacent relatively moving part. The dust ring 56,

mentioned above, also serves to retain the dust.

An important feature of this machine resides in the symmetry of the parts. The opposite hammerfaces and the opposite anvil and scoop surfaces are the same. By reason of this symmetry it is possible to operate the machine by rotation in either direction; so4 that when one set of faces and surfaces wears out, use may be made of the opposite faces and surfaces by running the machine in the opposite direction.

I claim:

l. In a crushing apparatus of the type having a hammer-supporting rotor surrounded by a relatively rotating screening cage mounted substantially concentrically with the rotor and arranged toraise and then drop the material into the hammer circle to be fractured by the hammers, the improvement which consists in forming the cage as a series of spaced anvils extending substantially parallel to the axis of rotation of the rotor and positioned uniformly around the cage with outwardly extending pocket surfaces intervening' each of said pocket surfaces having a substantial 1 portion thereof perforated and inclined to position such perforated portion to extend generally directly across the path of the fractured material projected from the hammers, whereby material impacting against the anvils finds a relativelyl large screeningarea immediately adjacent thereto for removing the fractured product from the cage. v

2. The apparatus as set forth in claim 1 in which the pocket surfaces are so spaced and positioned with relation 'to each other as to expose atleast some of the apertured area of each thereof directlyacross the path of the material projected by the hammers, so that such apertured areas of said'pocket surfaces act both to frac-v ture said material by impact substantially perpendicularly to the direction of travel of said material and to screen the fractured'product.

3. A crushing apparatus of the type having a hammer-supporting rotor surroundedby a relatively rotating screening cage mounted substantially concentrically with the rotor and arranged to raise and then drop the material into the hammer circle to be fractured by the hammers, in which the cage is formed by a series of spaced anvils extending substantially parallel to the axis of rotation of the rotor and positioned uniformly around the cage and by a plurality of outwardly extending pocket surfaces, one intervening between-and filling in each space between successive anvils, each of said pocket surfaces having a substantial portion thereof perforated with such perforated portion formed and positioned to be substantially perpendicular to the travel of the material projected by the hammers throughout a range of angles at which the hammers project such material toward such pocket, and with each of said perforated portions so distanced from the hammers that the material projected toward it by the hammers is fractured thereagainst by impact, whereby said perforated portions of said pockets serve both to fracture said material by impact substantially perpendicular to the direction'of travel of the hammer-projected material and to screen the fractured product out of said cage.

4. In a crushing apparatus of the type having a hammer-supporting rotor surrounded by a relatively rotating screening cage mounted substantially concentrically withthe rotor and arranged to raise and then drop the material into the hammer circle to be fractured by the hammers, a screening cage therefor formed of `end plates, a plurality f anvil bars securing said end plates together and serving as anvils to break the material projected thereagainst by the hammers, said anvil bars being spaced uniformly around the end plates and equi-distant from the axis of said screening cage and having the material-impact surfaces thereof substantially perpendicular to the direction of travel of the material projected thereagainst by the hammers, and aplurality of outwardly bulging screening sections secured to said ""end platesrand closing the spaces between said anvil bars, said anvil bars being so spaced'as to expose the screening sections, for a substantial distance thereon extending from said anvil bars, to the impact of the hammer-projected material, said impacted portions of said screening sections extending outwardly from the respective anvil bars substantially perpendicularly to the travel of the hammer-projected material throughout a range of angles at which the hammers project such material thereagainst, whereby the material projected by the hammers is fractured by substantially perpendicular impacts against the anvil bars and screening sections, with the impacted portions of said screening sections serving not only to fracture said material by impact but also to screen the fractured product out of said cage.

5. In a crushing apparatus of the type having a hammer-supporting rotor surrounded by a relatively rotating screening cage mounted substantially concentrically with the rotorand arranged to raise and then drop the material into the hammer circle to be fractured by the hammers, a screening cage therefor formed of a plurality of similar screening sections each of which is apertured to pass material below a predetermined size, and bulges symmetricallyvoutwardly on each side of a middle, substantially V-shaped apex, said apexes being spaced uniformly around the cage at a radial distance from the hammer tips which is uniform and less than half the radial distance from the hammer tips to the outer portions of such screening sections, substantial portions of said screening sections, containing said apertures distributed thereover, being so inclined and the apexes of said screening sections being so spaced from each other as to position such portions of said screening sections generally directly across the path of and exposed to the fractured material projected from the faces of the hammers during the appropriate directions of rotation of the hammers and cage, whereby the roles of the two symmetrical parts of each of said screening sections are interchangeable merely by reversing the directions of rotation of the cage and hammers.

6. In a crushing apparatus of the type having a hammer-supporting rotor surrounded by a relatively rotating screening cage mounted substantially concentrically with the roton and arranged to raise and then drop the material into the hamer circle to be fractured by the hammers, a

screening cage therefor having a plurality of anvil -bars positioned uniformly and at equal radii around the cage, and serving as anvils to break by impact the material projected thereagainst by the hammers, and a continuously curving outwardly bulging screening surface positioned between each two adjacent anvil bars closing the space therebetween, each of said screening surfaces having apertures therein for passing material below a predetermined size and being symmetrical with respect to a radial plane midway between the anvil bars at the ends of the corresponding screening surface, said anvil bars being so spaced circumferentially as to expose the screening surfaces to the impact of the hammerprojected material for a substantial distance thereon from the anvil bars, and being spaced radially from the ends of the hammers a distance less than half the radial distance from the ends of the hammers to the centers of said screening surfaces whereby the anvil bars and screening surfaces of the cage operate in similar fashion for either direction of cage rotation in raising and then dropping the material into the hammer circle, in fracturing by impact the material projected by the hammers and in screening the fractured product.

7. Crushing apparatus as set forth in claim 3 having an end feed supplying uncrushed material longitudinally to said rotor and comprising an entrance chamber in advance of said rotor coxinected to and rotating with said cage to supply said material to the lower portion of said cage, having said perforations on the pocket surfaces adapted Yto pass inmediately fractured material below a predetermined size and larger 'than the -nally desired size, having an outer screen of frusto-conical shape surrounding said cage and directly receiving said 4fractured material discharged through said cage, said outer screen passing thevflnally sized particles of the crushed material while retaining and feeding the remainder of the crushed material backward toward the entrance end of the apparatus, and having a connecting passage leading from said outer screen to said entrance chamber and acting automatically to return the oversized material from said outer screen to said chamber so that it will be discharged on to the uncrushed material therein, whereby the smaller particles are promptly removed from the cage so as not to interfere with the impact action therein and so as not to be subjected to further reduction before screening for size.

8. Crushing apparatus adapted to crush material to predetermined nal size comprising a rotor having a series of rows of hammers, an end feed passing uncrushed material longitudinally to saidy rotor, an inner .rotary screen receiving said material at its end and lifting -it and dropping it into the hammer circle of said rotor and having perforations adapted quickly to pass fractured material below a predetermined size larger than the finally desired size, an outer, finer rotary screen coextensive with and concentrlcally surrounding said inner screen and directly receiving said fractured material discharged-from said inner screen and immediately freely delivering the finally sized crushed material outward while retaining the remainder ofthe crushed material above said predetermined nal size, and

means for automatically collecting the retained oversize material from the inside of said outer screen and discharging it onto the uncrushed material in said end feed on the way to said rotor so that it will be lifted with said uncrushed material -by said inner screen and dropped into the hammer circle for recrushing, with the inner screen being formed with a plurality of outwardly bulging screening pockets in which a portion of each screening pocket serves as a scoop to lift the material and drop it onto the hammer circle and another portion of each screening pocket serves to fracture by impact the material projectedthereagainst by the hammers, both such.

portions of each screening pocket being apertured to pass therethrough material substantially larger than the size of the desired nal product.

STANLEY D. HARTSHORN. 

